1. Field of the Invention
This invention relates to apparatus for effecting liquid development of discrete latent electrostatic or photographic images.
2. Description of the Prior Art
It is well known to apply a liquid composition to a surface of a support material for developing latent electrostatic or photographic images thereon. A single liquid, usually referred to as a monobath, can be used to develop latent photographic images, whereas a liquid developer which comprises a liquid carrier and toner particles can be used to develop latent electrostatic images. On the other hand, developer and fixer solutions, as well as water, or various processing gases can be introduced sequentially into the apparatus to develop a photographic latent image in a well known manner.
In various types of apparatus known in the prior art, the development liquid can be confined to only the image area of the support material. The support material is clamped in position relative to a processing or developing head to form a development cell, and a single or a number of liquids are then applied sequentially to the surface bearing the latent image. Such processing or developing of a latent image can also include in its cycle of operation, the application to the image area of air for drying the previously applied liquid, or of a liquid which will displace the processing solutions because of its repellent characteristics. Representative prior art U.S. patents of the type described include U.S. Pat. No. 2,582,182 (issued Jan. 8, 1952 to C. M. Tuttle et al), U.S. Pat. No. 3,149,550 (issued Sept. 22, 1964 to Lohse et al) and U.S. Pat. No. 3,936,854 (issued Feb. 3, 1976 to D. S. Smith).
According to some prior art apparatus, the development cell includes a first member having an open-end chamber that is interconnected to a reservoir for at least one developing liquid and is provided with sealing means for retaining the developing liquid in proper relation to the image area being developed. The sealing means comprises at least one peripheral member that engages the latent image-bearing surface when the support material is arranged in the developing apparatus. A second member is movable relative to the first member for clamping the image-bearing support material therebetween via the sealing means. The first member is provided with suitable ducts so the developing liquid is directed as a flow over the support material or, more specifically, over the image area and within the confines of the sealing means. After the developing liquid has been applied for developing the latent image, air under pressure can be directed into the chamber to flow over the image area and discharge through a duct or ducts. The application of air under pressure squeegies any remaining liquid off the surface of the support material and carries it away through the ducts in a mist or in a finely atomized condition.
In development cells used in photographic and electrographic processes for developing latent images, a problem arises with respect to residual developer compositions (e.g., toner in electrographic processes) which are retained in the cell and build up after a period of time so as to reduce efficiency of the development process. An especially critical developer build-up problem occurs on the development electrode of electrographic processors where toner build-up rapidly occurs and causes electrical field problems from the electrode to the image. As a partial solution to this situation, it has been proposed to provide cross-flow of the developer and the air used to dry the developed image. Air applied to the image surface at right angles to the flow of developer more completely removes residual toner or other residual chemicals. However efficient such cross-flow apparatus, or any other apparatus designed to remove developer from the cell, is, there will still remain some developer in the cell which will build up over a period of time.
It has also been recognized that a venturi-forming member in the development cell, spaced closely to the image-bearing surface so as to define a shallow air passage across the surface face, effectively aids in the drying process. Of course, any residual developer build-up on this venturi-forming member would be critical because of its close proximity to the image-bearing surface, resulting in developer and/or air flow patterns on the developed image.